I have the Modine Hot Dawg (60K BTU) and very pleased with it.
Watch which BTU unit they are selling you. Most “Basic” units are 30-45K BTU. I suggest you get a 60K BTU unit or higher. For the couple hundred dollars more, you will be more pleased with the performance.
Also, a sealed or seperate combustion chamber is a must have feature (also most building coddes require it)
Typical cost is $200-300 for gas piping, $35-60 for dedicated electrical outlet, $1,000 plus mark-up on the unit. (Go with a 60 – 75K BTU) and add for your venting.
Some of our reputable competitors use a reznor. I’m not personally familiar with them.